The field of the invention is enclosures for electrical equipment, and particularly, enclosures which include a sealing well for sealing electrical equipment from the surrounding environment.
There are numerous applications where electrical devices such as pushbuttons, pilot lights and similar devices must be sealed off from the surrounding environment. Such seals may, for example, exclude liquids such as water where equipment is exposed to the weather or must be washed down such as in food processing plants, or where an enclosure may inhibit the passage of gases when the equipment is exposed to volatile vapors. Standards have been established for enclosure seals of various types and it is, of course, an objective in the art to meet these standards.
An example of such device may be found in the disclosure of U.S. Pat. No. 4,158,757 granted to Reichert et al. and assigned to the same assignee as the present invention. That particular patent is directed to a seal for an enclosure which includes a metal frame clamped between sealing surfaces on the base member and on an enclosure cover. This may be in the form of a separate frame or may include a frame integrally formed as part of a sealing well.
The present invention is directed to a sealing well which may or may not include the particular sealing concept disclosed in the aforementioned U.S. Pat. No. 4,158,757. In that particular patent, the construction provides a dual function in including an elastomeric ring in combination with a metal frame to provide "metal-to-metal" seal as required in certain standards, and which further satisfies the requirements of other standards for enclosing electrical equipment.
A sealing well, used in combination with a base of an enclosure, reduces installation costs associated with conventional conduit sealing fittings and provides a facile means of installing equipment and connecting the same with powerline conduit and wiring. A typical example of a sealing fitting, which may be eliminated by using a sealing well, may be found in U.S. Pat. No. 4,216,349 granted to Wium. Though these sealing fittings satisfy the electrical standards for effecting the necessary seal of the interior of the conduit, they are not without problems. In the first place, the fitting occupies considerable space and may still require more space for installation, neither of which may be available in cramped quarters. Further, the fittings are sometimes more expensive than the enclosure itself, and thus adds substantially to the cost of the installation.
It is quite often the practice to provide pre-wired sealing wells, and whether pre-wired or field wired, such sealing wells are not without their own problems. That is, the cavities of prior sealing wells were necessarily made relatively shallow to accommodate wiring connectors, such as so-called "wire nuts" disposed between the base of the enclosure and the bottom of a cup-like sealing well seated within the enclosure cavity. This shallow construction obviously limited the length of electrical devices residing within the cavity of the sealing well.